{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-5477", "assignerOrgId": "50d2cd11-d01a-48ed-9441-5bfce9d63b27", "state": "PUBLISHED", "assignerShortName": "wolfSSL", "dateReserved": "2026-04-03T07:59:59.388Z", "datePublished": "2026-04-10T05:06:22.884Z", "dateUpdated": "2026-04-10T05:06:22.884Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "50d2cd11-d01a-48ed-9441-5bfce9d63b27", "shortName": "wolfSSL", "dateUpdated": "2026-04-10T05:06:22.884Z"}, "title": "Prefix-substitution forgery via integer overflow in wolfCrypt CMAC", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-190", "description": "CWE-190 Integer overflow or wraparound", "type": "CWE"}]}], "affected": [{"vendor": "wolfSSL", "product": "wolfSSL", "modules": ["wc_CmacUpdate"], "programFiles": ["wolfcrypt/src/cmac.c", "wolfcrypt/src/aes.c"], "versions": [{"status": "affected", "version": "0", "lessThanOrEqual": "5.9.0", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "An integer overflow existed in the wolfCrypt CMAC implementation, that could be exploited to forge CMAC tags. The function wc_CmacUpdate used the\u00a0guard `if (cmac->totalSz != 0)` to skip XOR-chaining on the first block (where digest is all-zeros and the XOR is a no-op).\u00a0However, totalSz is word32 and wraps to zero after 2^28 block flushes (4 GiB), causing the guard to erroneously discard the live CBC-MAC chain state. Any two messages sharing a common suffix\u00a0beyond the 4 GiB mark then produce identical CMAC tags, enabling a zero-work prefix-substitution forgery. The fix removes the guard,\u00a0making the XOR unconditional; the no-op property on the first block is preserved because digest is zero-initialized by wc_InitCmac_ex.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "An integer overflow existed in the wolfCrypt CMAC implementation, that could be exploited to forge CMAC tags. The function wc_CmacUpdate used the&nbsp;<span>guard `if (cmac-&gt;totalSz != 0)` to skip XOR-chaining on </span><span>the first block (where digest is all-zeros and the XOR is a no-op).&nbsp;</span><span>However, totalSz is word32 and wraps to zero after 2^28 block flushes </span><span>(4 GiB), causing the guard to erroneously discard the </span><span>live CBC-MAC chain state. Any two messages sharing a common suffix&nbsp;</span><span>beyond the 4 GiB mark then produce identical CMAC tags, enabling a </span><span>zero-work prefix-substitution forgery. The fix removes the guard,&nbsp;</span><span>making the XOR unconditional; the no-op property on the first block is </span><span>preserved because digest is zero-initialized by wc_InitCmac_ex.</span>"}]}], "references": [{"url": "https://github.com/wolfSSL/wolfssl/pull/10102"}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "HIGH", "baseScore": 8.2, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"}}], "credits": [{"lang": "en", "value": "Calif.io in collaboration with Claude and Anthropic Research", "type": "finder"}], "source": {"discovery": "EXTERNAL"}, "x_generator": {"engine": "Vulnogram 1.0.1"}}}}

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{"cveTags": [], "descriptions": [{"lang": "en", "value": "An integer overflow existed in the wolfCrypt CMAC implementation, that could be exploited to forge CMAC tags. The function wc_CmacUpdate used the\u00a0guard `if (cmac->totalSz != 0)` to skip XOR-chaining on the first block (where digest is all-zeros and the XOR is a no-op).\u00a0However, totalSz is word32 and wraps to zero after 2^28 block flushes (4 GiB), causing the guard to erroneously discard the live CBC-MAC chain state. Any two messages sharing a common suffix\u00a0beyond the 4 GiB mark then produce identical CMAC tags, enabling a zero-work prefix-substitution forgery. The fix removes the guard,\u00a0making the XOR unconditional; the no-op property on the first block is preserved because digest is zero-initialized by wc_InitCmac_ex."}], "id": "CVE-2026-5477", "lastModified": "2026-04-10T06:16:05.243", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 8.2, "baseSeverity": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "facts@wolfssl.com", "type": "Secondary"}]}, "published": "2026-04-10T06:16:05.243", "references": [{"source": "facts@wolfssl.com", "url": "https://github.com/wolfSSL/wolfssl/pull/10102"}], "sourceIdentifier": "facts@wolfssl.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-190"}], "source": "facts@wolfssl.com", "type": "Secondary"}]}

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